This invention relates to a cellulose filter media useful in normal swimming pool and spa filtration applications.
The motion picture industry helped pioneer the use of Diatomaceous Earth (D.E.) for filtering swimming pools. Filming underwater requires high water clarity for good visibility. Conventional flocculation and filtration through high rate sand units, available in the 1930""s could not clarify the water sufficiently for quality filming. So, the industry experimented with D.E. media to improve the filtration process and achieve the desired underwater effects.
Many different types and styles of D.E. filters are available. Some are designed to be pressure backwashed. Saturated D.E. is flushed from the tank with water flow reversal, many utilizing an integral backwashing valve. Others feature easy internal access with quick opening band clamps and must be manually cleaned. Still other have filter bundles of square flat grids, curved filter grids, circular disks, or filter tubes. The health risk associated with the use of D.E., however, is free crystalline silica dust. Packages of D.E. now carry carcinogenic warning labels.
The oils (body oils, tanning oils, etc.) typically float on the surface of the water. In problematic pool and spa situations with high oil concentrations, significant quantities of oil simply flow through the filter and return to the vessel. This creates the illusion of lower long term operating pressures since so much of the light oils are not being trapped by the D.E. In fact, however, the oils that are trapped by the D.E. tend to bond the filter cake to the grids and eventually impregnate the grid material itself. The end result is large volumes of water needed to backwash (incompletely) the D.E. from the grids, fouled grids and increasing buildup of D.E. at the bottom of the filter. Unremoved oils will result in scum lines in the pool/spa and reduced water clarity. Continued operation with D.E. will require filter tear down, clean out and grid degreasing on a regular basis due to rising start-up pressure after each backwash. One solution to D.E.""s carcinogenic properties, problematic oil removal and filter caking tendencies has been the industry""s use of cellulose filter media. Cellulose has a natural affinity for oils. Cellulose actually xe2x80x9cwicksxe2x80x9d the oils from the water, in lieu of merely trapping the oils as D.E. does. By absorbing the oils into the cellulose fiber cake, the oils are not permitted to reach the filter grid material, preventing filter fouling. Despite this improvement, heavy suntan oil usage and continuous backwashing of cellulose filter media continues to be a problem.
This composition is a combination of powdered cellulose and an effective amount of at least one water insoluble, immobilized water treatment additive. Preferably, it is a filter media comprising powdered cellulose and an effective amount of at least one water insoluble, immobilized enzyme. Generally, the powdered cellulose is pulverized alpha cellulose and the immobilized enzyme is from the lipase category of very large, complex protein molecules. Preferably, the lipase enzyme has been transferred from a strain of Candida antarctica to a host organism of Aspergillus oryzae. The lipase enzyme consists of bead-shaped particles with a diameter in the range of 0.3-0.9 mm and a bulk density ranging from 400 to 450 kg/m3.
More preferably, the lipase enzyme shows 1,3 positional specificity or functions as a non-positional specific lipase. An acrylic resin immobilizes the enzyme. Preferably, a macroporous acrylic resin immobilizes the enzyme. Generally, the amount of immobilized enzyme ranges from 0.0001 to 0.10 weight percent. Preferably, the amount of immobilized enzyme ranges from 0.0001 to 0.01 weight percent. Specifically, the amount of immobilized enzyme is about 0.0225 weight percent.
The composition of this invention is a filter media composed of pulverized alpha cellulose (virgin) having an average (medium) fiber length of approximately to 60xcexc (microns). Typical degree of filtration is 2xcexc-5xcexc in normal swimming pool and spa filtration applications. The appearance of the material is a white, fibrous flock, with little to no odor. Powdered cellulose, has the GRAS (generally recognized as safe) status of the U.S.F.D.A. for use as a food additive. In terms of disposal after use, it is biodegradable when it is backflushed from the filter.
Because the composition is composed of powdered cellulose as produced from virgin pulp stock, the filter media has a natural affinity for oils. To assist with the removal of body and tanning oils, lotions, etc. from typical pool water, it is enzyme enhanced. Blended into the product is an immobilized lipase (oil breaking) enzyme. This enzyme is water insoluble and remains in the filter media for continuous treatment of the pool water filtrate.
Enzymes are natural occurring protein molecules, active in such processes as composting, organic decomposition and food digestive processes. The enzyme blended into this composition is water insoluble, which means that the enzyme remains in the filter cake for continuous action and is not circulated into the pool. Typical enzyme xe2x80x9cactivityxe2x80x9d for 6 months or more, resulting in a time released activity throughout the life of the filter media. Because the immobilized enzyme utilized is a food grade material and in a relatively low concentration, it remains a very safe, environmentally xe2x80x9cfriendlyxe2x80x9d product.
Other additives we can use alone or in combination with the enzymes include pH stabilizers, time release oxidizers, chemical stain removers, clarifiers, co-agulants, water conditioners and adsorptive materials.